Compensating device for rotary pumps



March 18, 1947. 5, PARSONS 2,417,701

PBNSA'HNG DEVICE FOR ROTARY PUIPS- Filad July 17, 1944' Patented Mar. 18, 1941 UNITED STATES PATENT or ice 2,411,701 oomnuss'rmo navrch FOR ROTARY PUMPS John B. Parsons, Toledo, Ohio Application July 17, 1944, Serial No. 545,214

2 Claims. (01. 103 -126) 1 This invention relates to pumps but more particularly to rotor pumps of the type having two rotors or gears, one of which is within-and eccentrio to the other, having tooth divisions, with 2 Figure 4v is a transverse sectional view on the line 4-4 of Figure 1; and

Figure 5 is a view similar to Figure 4 but with the flexible ported plate removed.

The illustrated embodiment of the invention comprises a rotary pump having a housing l0 formed with an inlet Ii and an outlet l2, both metallic surface, which serves as a sounding board. Although attempts have been made to rectify this condition, so far as I am aware no one heretofore has successfully coped with the condition.

An object is to overcome the above dimculties and to produce a pump of the above type in which the discharge line is free from noisy puleating sounds.

Another object is to produce a compensating device for a pump of the above character for militating against surging action of the pressure fluid in the region of the outlet and effecting substantially uniform continuous flow of fluid from the P p.

A further object is to equip a pump of the above character with a simple and inexpensive device which militates against noisy pulsations in the discharge lineby controlling the fluid discharge at the pump in such manner that a more uniform flow of fluid under pressure is obtained;

, 3 A still further object is to produce a flexible discharge valve disc for a pump of the so-called "Gerotor type which not only effects a more uniform fluid flow but also provides a bearing for one end of the pump rotors.

Other objects and advantages of the invention will hereinafter appear and for purposes of illustration but not of limitation, an embodiment of the invention is shownvon the accompanying of which are at one end of the housing and communicate with arcuate ports Ma and l2a respectively, which open into the pump chamber H3. The opposite end of the housing is closed by a cap it, which is held in place by screws and is formed with a central aperture through which extends a driving shaft it. Keyed to the end portion of the driving shaft it is a toothed male rotor it, which is surrounded by a toothed female rotor ii. The rotor it has a running fit within the pump chamber it. The female rotor H has one more tooth than the number of complementary shapediteeth on the male rotor, which is mounted eccentrically with respect to the female rotor, moves the same ahead of it progressively and continuously forming suction and compression phases which are timed with respect to the inlet and outlet ports lid and Ma respectively, thus to provide a substantially continuous how of fluid under pressure from the pump. The rotors are provided with contours, such that the teeth in theory wipe or make continuous travelling contact over those of the other during rotation. It is to be understood that the above described pump is old in the art, is available on the market under the name "Gerotor and the above brief description is deemed sumcient for 5 a full understanding of the invention.

As a practical matter a pump of the above description has not been satisfactory for many installations because of the pulsating noise, which it makes in operation. It would appear theoretically possible to overcome thisobjection ii the conditions in all cases were the same. For example, if the pump were operated only at a certain specified speed and ii the viscosity 0! the fluid were always the same, then empirically the 5 proper size 0! the ports might be determined so that noisy operation would be eliminated. However, that, would be most difiicult, expensive and troublesome and consequently such objection definitely militates against the wide usefulness of the pump as a general purpose machine and one which 'can be employed to advantage in regions, where the expense of extended experimental and profound engineering workv to determine the correct port area is not feasible.

The cause of the noisy operationo! the pump rotor H, the arrangement being such that the fluid trapped in the cavity a: is about to be opened to the adjacent edge of the port l2a. If the cavity a: were entirely filled with pressure fluid, then the discharge thereof through the port l2a would currently'obtained, then the pump would operate substantially free from objectionable pulsating noise. However, as a practical matter, due to the speed at which the pump operates andthe viscosity of th fluid, in particular liquid, being handled, the cavity a: and its subsequent counterparts, are often not entirely filled with liquid but have a certain volume of air with it which, when compressed, discharges in a surging manner through the discharge port l2a. On the other hand, these cavities or some of them may have a partial vacuum in which case a reverse action takes place momentarily at th instant the discharge port l2a is encountered. ,The conditions may alternate but in any event, it is believed that they cause the objectionable surging or throbbing noises incident to the operation of the pump and militate against the creation of a continuous uniform flow of liquid through the discharge pipe or tube.

In order .to cope with the abov problem, a relatively thin flexible resilient disc l8 of sheet material, preferably metal is placed over the discharge end of the pump. It has approximately the same diameter as the rotor l1 and has arcuately shaped inlet and outlet ports l9 and 20 respectively. The disc is held against rotation by a tab 2| which flts into a suitable notch in the housing Ill. The disc i8 is very thin, as for example of the order of .010 inch and since it also serves as a thrust or bearing plate, it is preferably of spring bronze, when the pump parts are of steel. Y

'The-inlet port opening it is of the same size as the port Ila in the pump housing but the port 20 is smaller thanthe discharge port l2a. Referring to Figure 4, it will be observed that a portion of the disc l8 covers part of the port l2a in the region of the fluid inlet side. It will be understood that the-rotor parts are moving in a counterclockwise direction and the portion of the port l2a at theleft of Figure 4 is covered by the spring disc l8.- In this manner an exposed portion 22 ofthe spring disc It appears upon looking into the pump housing through the port I211. The positioning of the portion 22 is such that the discharg of liquid into the port l2a is slightly delayed enabling an approximate .be as desired and, provided this condition re- 4 equalization in pressure between the liquid in the cavity a: and the cavity directly in advance of it. The exposed portion 22 is sufficiently flexible' and resilient so that by a slight flexing movement thereof due to pressure build-up within the cavity, escape of fluid into the discharge line may be delayed so that uniform flow from thepump is effected and surging or flow of fluid from the discharge line to the pump is prevented.

Thus in operation the portion 22 of the disc flexes to afford fluid discharge from the pump.

valve-like portion 22 may be moved ahead or rearwardly for changed conditions. For example, it may be moved rearwardly if the speed of the pump is increased or liquid of greater viscosity is employed. On the other hand, it may be moved forwardly if the pump operates more slowly and the liquid is of less viscosity. However, in the main the important feature is to cover the point of discharge from the indicated cavity a: so as to eliminate the recurrent pounding or surging in the discharge line.

It is to be understood that numerous. changes in details of construction, arrangement and operation may be effected without departing from the spirit of the invention especially as defined in the appended claims.

What I claim is:

1. Compensating device for a pump having mating toothed pump rotor members arranged one within the other and fluid inlet and outlet ports associated therewith, comprising a relatively thin disc of spring metal abutting one end of said pump rotor parts to provide a bearing therefor, said disc having in an outlet port overlying the pump outlet port, the trailing edge of said disc outlet port being advanced relative to the pump outlet port and with respect to the direction of rotation of the pump rotor members to form a valve-likeportion adapted to flex in response to diiferences in fluid pressure in the adjacent portion of the pump and in the discharge line, and means clamping the peripheral portion of said disc throughout the circumference thereof to hold same from flexing movement.

2. Compensating device as claimed in claim 1, comprising means for holding said disc against turning movements.

JOHN B. PARSONS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,053,919 Pigott' Sept. 8, 1936 

